Oxymethylene polymers, which include polyoxymethylene homopolymers and polyoxymethylene copolymers, possess many useful properties and characteristics. For example, the polymers can have great strength properties while also being chemical resistant. The polymers can also be easily molded into any desired shape. The polymers are currently being used in all different types of applications. For instance, polyoxymethylene polymers are being used to form interior or exterior automotive parts, parts for consumer appliances, parts for industrial processes, and the like.
Oxymethylene polymers can be produced via anionic polymerization of anhydrous formaldehyde or can be produced through the cationic polymerization of formaldehyde or cyclic oligomers, such as trioxane. During cationic polymerization, the polymer can be formed in bulk (i.e. without solvent). Alternatively, the polymerization can take place in solution where the polymer precipitates in a solvent to form a heterogeneous phase. In still another embodiment, a majority of the polymer may be formed in the heterogeneous phase followed by further polymerization in a homogeneous phase.
During the formation of oxymethylene polymers, cationic initiators are typically combined with one or more monomers to initiate polymerization. After polymerization, the reaction mixture can be rapidly and completely deactivated by adding a deactivator.
The deactivator can be added to a heterogeneous phase after the polymer has precipitated in a solvent, or can occur during a homogeneous phase, while the polymer is in a melted form. After being deactivated, the resultant polymer can be ground and/or pelletized. In some embodiments, the polyoxymethylene polymer is compounded with various different components in order to produce a master batch. The master batch can then be combined with greater amounts of polyoxymethylene polymer resin or other ingredients during a molding process to produce various products.
During the production of polyoxymethylene polymers, some scrap material is produced that is comprised primarily of the polyoxymethylene polymer. Since recycling of the waste products coming from production and compounding of the polymer is beneficial, in the past, various different processes have been proposed in order to recycle the polymer. In one embodiment, for instance, the reclaimed polyoxymethylene polymer is converted into an aqueous solution of formaldehyde. The aqueous solution of formaldehyde can then be used to produce various products, such as trioxane. Recycling polyoxymethylene polymers in this manner, however, is not cost effective. In addition, conversion of the polymer into trioxane is relatively low.
In view of the above, a need currently exists for a process of recycling polyoxymethylene polymers. In particular, a need exists for a process for recycling polyoxymethylene polymers and converting them into usable monomers, such as a cyclic acetal.